2. LWMQN Channels: Topics and Messages

What is LWMQN Channels

LWMQN is equipped with several channels to implement the LWM2M interfaces based on MQTT pub/sub approach. These channels are simply MQTT topics, and such special topics are named as channels to distinguish from generic topics. The LWMQN Client/Server messaging is based on these channels.

Under the Hood

1. Special Topics for LWMQN Channels
2. Message through the Channel
3. Data Type Summary of Messages

---

1. Special Topics for LWMQN Channels

Channel	Client Pub / Server Sub	Client Sub / Server Pub
register	register/${clientId}	register/response/${clientId}
deregister	deregister/${clientId}	deregister/response/${clientId}
update	update/${clientId}	update/response/${clientId}
shcedule	shcedule/${clientId}	shcedule/response/${clientId}
ping	ping/${clientId}	ping/response/${clientId}
announce	-	announce
request	-	request/${clientId}
response	response/${clientId}	-
notify	notify/${clientId}	notify/response/${clientId}

************************************************* ### 2. Message through the Channel

Channel	Client Pub	Server Pub
register	{ transId, lifetime, ip, mac, version, objList }	{ transId, status }
deregister	{ transId }	{ transId, status }
update	{ transId, lifetime, ip, version, objList }	{ transId, status }
shcedule	{ transId, sleep, duration }	{ transId, status }
ping	{ transId }	{ transId, status }
announce	-	Any thing can be serialized which depends on implementation
request	-	{ transId, cmdId, oid, iid, rid, data }
response	{ transId, cmdId, status, data }	-
notify	{ transId, oid, iid, rid, data }	{ transId, status }

---

3. Data Type Summary of Messages

Property	Data Type	Description
transId	Number	A numeric id for each transaction, e.g., 102
lifetime	Number	Lifetime of the device. If no message comes from the device within lifetime seconds, the server will deregister this device from the network, e.g., 6000 (secs)
ip	String	Device ip address, e.g., '192.168.1.60'
mac	String	Device mac address, e.g., 'd8:fe:e3:e5:9f:3b'
version	String	LWMQN version, e.g., '0.0.1'
objList	Object	IPSO Objects and Object Instances live in the client. Each property in objList is an oid: [ iid, ... ] pair, e.g., { 3301: [ 0 ], 3302: [ 6 ], 3303: [ 0, 1, 18 ] }
sleep	Boolean	To tell server that this client is going to sleep (true) or waking up from sleep (false)
duration	Number	When a client is going to sleep, it can tell the server of how many seconds from now that this client will check in again
cmdId	Number	Command id, can be 0(read), 1(write), 2(discover), 3(writeAttrs), 4(execute), 5(observe), 6(notify), and 7(ping)
status	Number	Status code
oid	Number | String	Object Id, a numeric id is preferable for IPSO-deifned Object, e.g., 3303 for a temperature sensor. A string id is also accepted if the Object is not an IPSO-defined one
iid	Number | String	Object Instance Id, a numeric id is preferable but a string is also accepted
rid	Number | String	Resource Id, a numeric id is preferable for IPSO-deifned Resource, e.g., 5700 for a sensor value. A string is also accepted if the Resource is not an IPSO-defined one
data	Depends	Payload per request